Radioisotope Characteristics of isotope

LESSON 2 - Understanding nuclear

State of Types of Half-life
energy.
matter ray
Strontium-90 Solid Beta 28 years
Cobalt-60 Solid Gamma 5 years
Xenon-133 Gas Beta 5 days Atomic mass unit (a.m.u.)
Iodine- 131 Liquid Gamma 8 days
Polonium- 210 Solid Alpha 140 days The atomic mass unit (u) is the unit of mass for atoms and
subatomic particles such as the proton, neutron and
(i) Explain the suitability of the electron.
characteristics to be used in the
strelisation of medical equipment. 1 a.m.u or 1 u is 1 of the mass of the
(ii) Determine the most suitable radioisotope 12
to be used and give one reason for your carbon-12 atom.
choice.

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1 u = 1.66 x 10-27 kg
(c)Gamma rays can produce an effect on
photographic film. Example 1
Explain whether gamma rays is suitable to be

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used in taking photographs of an organ in The mass of an atom Cobalt-60 is 59.933820 u.
humans. What is the mass of the atom in kilogram?

(a) Beryllium- 11 isotope emits two rays. The Solution

isotope is placed in front of an electric field and

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the radioactive radiation path is shown in
Diagram32.2.
Nuclear Fission
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Nuclear fission is the splitting of a heavy nucleus into two
lighter nuclei, which subsequently emit either two or three
neutrons and release of large amounts of energy.
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The example of a nuclear fission is shown as follow:

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Diagram32.2

(i) Name both rays that are emitted by the When a uranium-235 is bombarded by a neutron , it is split
isotope. into two fission fragments (Kripton-131 and Barium-142 )
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and three free neutrons.

(ii) Explain why the rays follow the path
shown in Diagram32.2.
Another example of nuclear fission is :
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Chain reaction
A reaction that is self sustaining as a result of the products
of one step initiating a subsequent step.
In nuclear chain reactions the succession depends on the
production and capture of neutrons.
Thus, one nucleus of isotope uranium-235 can disintegrate
with production of two or three neutrons, which cause
similar fission of adjacent nuclei. These in turn produce
more neutrons which go off and split other uranium atom -
and so on.

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 Nuclear fusion is believed to be process by which energy is
released by the Sun. When two
hydrogen-2 nuclei moving at high speed collide, they can
join together to produce a heavier nucleus. A large amount
of energy is released.
The temperature of a gas must be high giving a high
average kinetic energy. Due to the requirement of high
temperature, nuclear fusion is also known as a
thermonuclear reaction.
Hydrogen bombs are made following the principle of
nuclear fusion.
Another example of nuclear fusion is :

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Nuclear Energy
A controlled chain reaction is used in nuclear power
stations while an uncontrolled chain reaction is used in

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According to Albert Einstein, In a nuclear reaction (nuclear
nuclear bombs. fission and fusion) neither mass nor energy are conserved
separately but they can exchanged one for the other and
Critical mass only the “mass-energy” is conserved. A loss of mass means
that the mass has changed to energy.
The minimum mass of fission material that will sustain a

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The relationship between the mass and the energy is given
nuclear chain reaction. by the equation:
For example , when a nucleus of uranium-235 disintegrates
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two or three neutrons are released in the process, each of
which is capable of causing another nucleus to disintegrate E = mc2
, so creating a chain reaction. However, in a mass of U-235
less than the critical mass, too many neutrons escape from Where E = energy released
the surface of the material without hitting , preventing a m= loss of mass or mass defect
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chain reaction from happening. c = speed of light = 3 x 108 ms-1

Example 2
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Polonium-210 undergoes alpha decay to become plumbum-

206 . The equation for the decay is:

210 206 4
Po → Pb + He + energy
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86 84 2

Additional information:
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Mass Po = 209.982 u
In the atom bomb, therefore, two or more sub-critical Mass Pb = 205.969 u
masses have to brought together to make a mass in excess Mass He = 4.004 u
of the critical mass before the bomb will explode. 1 u = 1.66 x 10-27kg
c = 3 x 108 ms-1
Nuclear Fusion
Using the equation and the information above , calculate
Nuclear fusion is the combining of two lighter nuclei to
(a) The mass defect
form a heavier nucleus with the release of large amount of
(b) The energy released in unit J and in unit of eV
energy.
(c) The power generated in 2 ms
The example of a nuclear fusion is shown as follow:
Solution

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Generation of electricity from nuclear energy – Nuclear
Power Station

The pros and cons of using nuclear fission to generate

electricity

Nuclear power is controversial. Here are some arguments

for and against using nuclear power station to generate
electricity.

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The energy released from nuclear fission can be used to
1. Nuclear power provides cheaper electricity than
generate electricity. A nuclear power station consists two
any other method because the nuclear power
main components:
stations need less fuel than stations which use
(a) Nuclear reactor
fossil fuels.

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(b) Generator
The price of nuclear fuel is more stable than
The main components of nuclear reactor :
fossil fuels.
Component Function Vast reserves of nuclear fuel in the world.
Graphite core Acts as moderator to slow down the
fast neutrons produced by the fission. 2. Safety procedures in the administration of nuclear

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In some nuclear power plant, the reactors are very advanced and safe.
moderator is water. Workers in nuclear power stations are at less risk
Uranium rod To produce nuclear power when the
KT than those in other energy industries. Many
(fuel) fission reactions occur in the uranium people have been killed in accidents in coal
rod mining and oil rigs; very few comparable
Boron control To control the rate of fission reaction. accidents have occurred in nuclear power
rod The control rods are lowered into the stations.
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reactor core to absorb some of the

neutrons and thus reduce the rate of 3. Nuclear power is clean because produces
the fission reaction. less waste than fossil fuels.
Sometimes the rod is made of Burning fossil fuels in power stations does more
cadmium damage to the environment than nuclear power
Coolant To take away heat from the nuclear stations. One of the major causes of acid rain is
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reactor. the sulphur dioxide and nitrogen dioxides

‘Heavy’ water and carbon dioxide are released from burning coal in power stations.
used as coolant because they have So nuclear power does not add to the greenhouse
high specific heat capacity. effect.
Concrete shield To prevent leakage of radiation from
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the reactor core 4. Produces useful radioisotopes as by-

The main components of generator : products that can be used in industry, medicine,
Component Function agriculture and research.
Steam To change water into steam when the
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generator water in the generator is heated.

The steam then drives the turbines
Turbine To turn the coils in the dynamo in the
electrical generator to produce
electricity

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 TUTORIAL 4

1 The process of a heavier nucleus splitting to

form two lighter nuclei is known as

A nuclear fusion
1. The initial cost to design and build a nuclear B nuclear fission
power station is very high. C chain reaction
Used fuel rods are very hot and highly
radioactive with very long halve-lives. 2 A Uranium-235 nucleus will split when it captures
Expensive procedures are required to cool down

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the rods and store them. A an alpha particle B a gamma ray
2. There is always a risk of accidents. If C a neutron D a proton
something goes wrong with a nuclear power
station , it is very much more serious than an 3 Which of the following nuclear reactions is an

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accident at a conventional power station. The example of fission?
effects cross national boundaries and can be felt
2
many hundreds of kilometers away. A 1H + 21 H → 4
2 He + energy
The hot water discharged from the nuclear 14 15
power stations can be caused thermal pollution. B 7N + neutron → 7N + energy

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People who work in the nuclear power station 214
→ 237
C 94 Pu 92 U + α + energy
and those living nearby may be exposed to
239
excessive radiations. D 92 U → 95 141
38 Sr + 54 Xe +
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3 neutrons + energy
The arguments about nuclear power do not lead to any clear 3 The diagram shows the start of a chain reaction.
conclusion. It is not the sort of question which can be
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resolved and answered by simply looking at the facts. For

some people one of these points is so important that it
outweighs all the others. No one can simply weigh up all
the evidence and arrive at the ‘right’ decision. There will
always be room for discussion and argument.
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Which nuclear reaction is taking place?

A Fission of hydrogen
B Fusion of hydrogen
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C Fission of uranium
D Fusion of uranium

4 It is possible for a chain reaction to occur in nuclear

fission because

A new neutrons are produced

B two fission fragments are produced
C a large amount of energy is released
D fission does not require a very high temperature

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5 What energy changes take place in a nuclear power
station? A nucleus fission B nucleus decaying
C nucleus fusion D nucleus
A Heat energy→ Mechanical energy → disintegration
Nuclear energy
B Nuclear energy→ Heat energy 12 In which type of nuclear reaction are the nuclei
→ Electrical energy heavier after the reaction than were before?
C Heat energy→ Nuclear energy
→ Electrical energy A α – decay B β - decay
D Mechanical energy→ Heat energy C Nuclear fission D Nuclear fusion
→ Electrical energy

6 In a nuclear reactor , the neutrons produced are 13 Which of the following is a fusion reaction?
slowed down by
A
2
H  21 H  23 He 01 n  Energy

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A Uranium rod B Graphite core 1
C Boron control rod B
226
88 Ra  222
86 Rn    Energy

7 In a nuclear reactor, the rate of the chain reaction is C

21
Na 12
21
Mg    Energy

20
11
controlled by
D
239
92 U  95
38 Sr  54 Xe 3 0 n  Energy .
141 1

A uranium rods B boron rods

C graphite core D concrete shield 14 In the sun, energy is released when hydrogen nuclei
collide and form heavier nuclei. This process is called

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8 In a nuclear reactor, moderator is used to
A Ionisation B Diffusion
A absorb slow neutrons
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C Fission D Fusion
B slow down the fast neutrons
C drive the steam turbine to generate electricity 2
D absorb radioactive emissions from the core of 15 What happen when two nuclei of deuterium ( 1H )
the reactor 4
fuse together to form a nucleus helium ( 2 He ) ?
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9 Which of the following is not true regarding to A Mass and energy are both created
function of components in a nuclear reactor? B Energy and mass are both lost
C Mass is converted into energy
Component Function D Energy is converted into mass
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A Control rod Control the rate of reaction 16 Which of the following is made by using the
B Concrete Prevent natural radioactive principle of nuclear fusion.
shield entering the reactor
C Moderator Slow down fast moving A Atom bomb B Hydrogen bomb
neutron C Nuclear reactor
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D Coolant To take away heat from the

nuclear reactor. 17 Which of the following is not the similarity between
10 Diagram shows a nuclear reaction. nuclear fission and nuclear fusion?
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A Both of the nuclear reactions experience mass

defect
B Both of the nuclear reactions produced a large
amount of energy
C Both of the nuclear reactions produced new
nuclei
D Both of the nuclear reactions require very high
temperature

The nuclear reaction is . 18 A nuclear reaction is given by the equation

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 X→Y+Z
Which of the following is correct?
(a) (i) Name the reaction that occurs.
A The nucleon number of X > The nucleon ………………………………………...
number of Y + nucleon number of Z (ii) State one conditions that is required for
B The proton number of X > The proton number the reaction in (a) (i) to occur.
of Y + proton number of Z ………………………………………...
C The atomic mass of X > The atomic mass of Y (b) (i) State the charges of 24 He
+ the atomic mass of Z
…………………………………………
19 In a nuclear fission reaction, an atom of U-235 is hit (ii) State the number of neutron in 24 He
by a fast moving neutron and 200 MeV nuclear ………………………………………...
energy is released. The nuclear energy released is in
the form of 26 A nuclear reaction is represented by the following

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equation:
A Nuclear energy B Heat energy 235 1 141 93 1
C U-235 atom D Moving neutron 92 U + 0n → 55 Cs + 37 Rb + X 0 n + energy

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20 The equation shows the decay of uranium-235 The information about the equation is shown as
follow:
235
92 U 231
90 Th  He 4
2 235
Mass of 92 U = 235.04392 u
1
0n
What is the mass that is converted to energy? Mass of = 1.00867 u

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141
[Mass of uranium-235 = 235.0439 u, Mass of 55 Cs = 140.91963 u
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mass of thorium-231 = 231.0363 u, 93
Mass of 37 Rb= 92.92157 u
mass of alpha particle = 4.0026 u ]
1 u = 1.66 x 10 -27 kg
A 0.0025 u B 0.0050 u Speed of light = 3.0 x 10 8 ms-1
C 0.0060 u D 0.0075 u
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(a) What is the value of X?

21 In a nuclear reaction, 5.265 x 10–10 J energy is ………………………………………………
released. What is the mass defect of this reaction? (b) Name the nuclear reaction involved.
………………………………………………
A 4.74 x 107 kg B 1.58 x 10–2 kg (c) What is the meaning of the nuclear reaction in
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C 1.76 x 10–18 kg D 5.85 x 10–27 kg (b)?

……………………………………………….
23 The mass defect in a nuclear reaction is ……………………………………………….
2 x 10 -3 kg. What is the released? ……………………………………………….
[ Speed of light = 3.0 x 10 8 ms-1] (d) State one application of the nuclear reaction in
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(b)
………………………………………………
A 1.8 x 10 14 J B 1.8 x 10 17 J
(e) Calculate
C 1.6 x 10 14 J D 1.6 x 10 17 J
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(i) the energy released .

24 The mass defect in a nuclear reaction is
0.05 u. What is the released?
[ Speed of light = 3.0 x 10 8 ms-1 , (ii) the power generated in 5 µs.
1 u = 1.66 x 10 -27 kg ]

A 2.55 x 10 -21J B 5.10 x 10 -19 J

C 3.83 x 10 -13J D 7.47 x 10 -12 J

27 Table 27.1 shows an equation of a reaction and total

atomic mass before and after a nuclear fission.

Nuclear fission
25 The following equation represents the reaction that
occurs in the core of the sun. Before reaction After reaction

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 239
Equation Pu + 1n 145
Ba + 93
Sr +
94 0 56 38

2 1n + Energy
0

Total atomic 240.06082 u 239.85830 u

mass
Table 27.1

Table 27.2 shows an equation of a reaction and total

atomic mass before and after a nuclear fusion.

Nuclear fusion
Before reaction After reaction You are required to investigate the characteristics of
2
Equation H + 3H 4
He + 1n + the features in the nuclear reactor as shown in Table
1 1 2 0
28.

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Energy

Total atomic 5.03013 u 5.01043 u Material Thickness

Material Material
mass Nuclear for the of
for the for the

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Reactor control concrete
Table 27.2 moderator coolant
rod shield

(a) (i) What is meant by a nuclear fission ? Graphite Krypton Oil Thin
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(ii) Using only the information given in Iron Boron Oil Thin
Table 27.1 and Table 27.2, compare Q
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nuclear fission and nuclear fusion. Hence Heavy
state the relationship between mass and Graphite Boron Thick
R water
energy involved.
Heavy
(b) Nuclear fission produces a chain reaction. Iron Krypton Thick
S water
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Describe how the chain reaction happens in a

nuclear fission of an atom of uranium.
Table 28

Explain the suitability of each characteristic of the

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28 (a) Diagram 28.1 shows how a system is used in a features in the nuclear reactor which can generate a
factory to ensure the thickness of paper sheets controlled nuclear reaction safely.
are uniform. The system uses radioisotope as Determine the most suitable reactor to be used.
the radioactive source. Give reasons for your choice.
(c) A nuclear reaction is represented by the following
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equation:
235 1 141 93 1
92 U + 0n → 55 Cs + 37 Rb +2 0n + energy
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The mass defect produced in the reaction is

0.19585 u.
[1 u = 1.66 x 10 -27 kg]

Calculate,

(i) energy released

(ii) power generated in 5 µs.
Diagram 28.1

(i) What is the meaning of radioisotope?

(ii) Based on Diagram 28.1, explain how the
system can be used to ensure the
thickness of the paper is uniform?
(b) Diagram 28.2 shows a nuclear reactor which is
used to generate nuclear energy.

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